Soil Soil Formation 1 The four major components

Soil

Soil Formation 1. The four major components of soil are: Water (25%) Air (25%) Organic matter (6%) Parent material (44%) 2. Parent material is: Bedrock which provides mineral content of the soil, Ex: Sand, silt and clay • Quartz: Si. O 2 • Calcite: Ca. CO 3 • Feldspar: KAl. Si 3 O 8 • Mica (biotite): K(Mg, Fe)3 Al. Si 3 O 10(OH)2

3. How is soil made from parent material? Include the role of weathering and living organisms • Weathering (physical and chemical) creates small pieces • Dead organisms- decay and release nutrients and gases • living organisms also release nutrients and gases Parent material can be native to the area or transported to the area by wind, water or a glacier EX: Calcareous soils in Miami-Dade County are derived from Miami limestone. Most of Miami-Dade County, part of Broward County, and Monroe County (including the Florida Keys). Broward also has marl and stone sand bedrock

4. Humus is: Organic matter Dead and decayed organisms, ex plant matter 5. How long does it take to make soil from bare rock? 10 000 years

Soil Profile 1. Describe the 5 Soil horizons • O- Organic matter, leaf litter (duff), dead animals, decomposed litter • A- Surface soil, decomposed organic matter and minerals, humus (fertile) • B- Subsoil, leached nutrients • C- Parent rock, weathered large unbroken rocks • R (Bedrock)- mostly a continuous mass of hard rock

Soil Texture 1. What is soil texture? • Proportions of clay, sand silt Ø Particle size Smallest - clay = less than. 002 mm - - Silt =. 002 mm -. 05 mm largest - sand =. 05 mm - 2 mm

2. What is porosity? • Ability to hold water 3. What is permeability? • Ability of water to flow through the material (rate) 4. Compare permeability of sand clay. Water • Sand high, clay low High permeability Water Low permeability

5. What is a loam? • A loam has about = mixtures of clay, sand, silt and humus - best for growing crops. 6. How can soil texture be determined? • Determined by particle size and feel

Soil type 1. What are the main Soil types? There are six main types of soil usually discussed in agriculture, distinguished by the size of the particle matter that makes up the soil. • Sandy (water/minerals easily flow) • Clay (no drainage) • Silty (fertile, good drainage) • Loamy (a mixture of soils) • Chalky (alkaline) • Peaty (acidic , undecomposed organic matter)

Table 10 -1 p. 216 Texture Nutrient Capacity Infiltration Water-Holding Aeration Capacity Clay Good Poor Silt Medium Medium Sand Poor Good Loam Medium Medium Refer to Fig. 10 -15 p. 215 Tilth

Soil Erosion is the process by which soil and rock are removed from the Earth's surface by wind or water flow, and transported and deposited in other locations. Ø Sheet erosion - surface water peels off fairly uniform sheets of soil. Ø Rill erosion - fast flowing rivulets cut Small channels in soil. Ø Gully erosion - rivulets join together to Cut wider, deeper ditches or gullies Two major impacts- loss of soil fertility and pollution of near by waters

Causes of soil Degradation 1. Deforestation No vegetation to hold the soil, soil is removed, loss of soil fertility, pollutes and can silt up rivers, decline in fish, flooding can worsen Management: prevent deforestation, manage forest harvesting, replant

(a) Selective cutting (b) Clear-cutting Clear stream (c) Strip cutting Muddy stream Uncut Cut 1 year ago Dirt road Cut 3– 10 years ago Uncut Clear stream Stepped Art Fig. 10 -6 a, p. 219

2. Agriculture Overgrazing- livestock are grazed on land in an unsustainable way (poorly managed) which leads to soil erosion and compaction of soil (due to the feet of the animals) • Solutions-Rotational grazing- land is not grazed on until the plants have had enough time to grow back, cattle supplied with other food sources, ex hay • Over grazing can lead to desertification

Soils Degradation Ø Desertification - combination of Prolonged drought and human activities Lead to a reduction in the productive potential of land. Solutions: Reduce 1. Overgrazing 2. Deforestation 3. Destructive forms of farming, irrigation, and mining

Soils: Degradation Ø Salinization - salts left on soil as irrigation water evaporates. Stunts crop growth and reduces crop yields. • Waterlogging - farmers leach salts from Soils by applying large amounts of water. if water does not drain, saline water sits in pools and damages roots of plants. Solution- Drip irrigation, better drainage

Prevention Reduce irrigation Switch to salttolerant crops (such as barley, cotton, sugar beet) Cleanup Flushing soil (expensive and wastes water) Not growing crops for 2 -5 years Installing underground drainage systems (expensive) Preventing and cleaning up soil salinization

Industrialized Crop Production Causes Soil Erosion • Industrialized agriculture, high-input agriculture (intensive) produces 80% of world’s food supply • Uses heavy equipment and large amounts of fossil fuels, water, commercial fertilizers, pesticides, and financial capital. • Primarily monocultures – single crop in one area. – Goal is to steadily increase crop yield, Ex Corn

Reduce Soil Erosion Due to Agriculture Soil conservation methods • Crop rotation- Crop rotation is the practice of planting different crops during consecutive growing seasons. By doing this the following benefits are applied to the soil and plants: • Strip cropping with cover crop

Terracing: Carving steep hills into terraces to retain water at each level and prevent soil erosion from downhill runoff. Contour farming: plowing rows to follow the curve of gently sloping land. Same benefits as terracing. Terracing

Alley cropping: rows of crops are planted between a row of trees that provide fruit or fuelwood and reduce Evaporation and wind blown soil erosion Windbreaks - use rows of trees to reduce wind erosion and help retain soil moisture.

Soil Degradation: conventional tillage Ø Conventional-tillage - fields often Plowed in the fall and left bare over winter. This leaves it vulnerable to Erosion, breaks soil structure Solution: Conservation tillage Idea is to disturb the soil as little as possible when planting crops No-tillage- leave last years crop, use Seed injectors Minimum tillage - subsurface soil is loosened but not topsoil.

CONSERVATON TILLAGE Advantages Disadvantages Reduces erosion Saves fuel Cuts costs Holds more soil water Reduces soil compaction Allows several crops per season Does not reduce crop yields Can increase herbicide use for some crops Leaves stalks that can harbor crop pests and fungal diseases and increase pesticide use Requires investment in expensive equipment

• Water Management Over-watering a crop area will result in erosion of soil and possible flooded fields. • To counteract this farmers can plant crops native to the area that do not require external irrigation or employ minimal water techniques, such as dripirrigation - the process of only watering the crops themselves by using a hose with small holes at each crop.

Case Studies MEDC- USA pg 303 textbook (Dustbowel 1930 s) LEDC- India see article

Types of Soil Characteristics Podzols are soils with an ash • Cool moist environment grey subsurface horizon, bleached by organic acids, on Climate: top of a dark accumulation • Evergreen so limited litter horizon with brown or black layer reddish iron compounds. • Slow to decompose due to • Podzols occur in the Boreal limited soil organisms (cold) and Temperate Zones Water: • Soils are acidic (pine • Lots of water, snow melt needles), little ground • Water infiltrates through vegetation layers, leaches out nutrients • Sandy not good for farming (Fe, Al) that collect lower down the profile.

Ø Soil horizons Ø Soil profile Immature soil O horizon Leaf litter A horizon Topsoil Regolith Bedrock B horizon Subsoil C horizon Young soil Parent material Mature soil